Python xlrd / xlwt creates a new workbook using sheets from two different books preserving formatting

Let me first explain my terminology. The Excel workbook has sheets. For example. new Excel workbook contains 3 sheets by default.

Now using xlrd, xlwt and xlutils, my goal is to output a new book (say: file3) by inputting 3 sheets from file1 and 1 sheet from file2. All of this preserves as much formatting as possible. I am using the following code (file1, file2 which you have to create manually yourself, just fill them with numbers AND text):

import os
import xlrd
import xlwt
from xlutils.copy import copy as xlutils_copy
from copy import deepcopy as deep_copy

new_workbook = xlwt.Workbook()

with xlrd.open_workbook("file1.xls", formatting_info=True) as rb1:
    wb1 = xlutils_copy(rb1)

    allSheets = []
    allSheets.append(wb1.get_sheet(0))
    allSheets.append(wb1.get_sheet(1))
    allSheets.append(wb1.get_sheet(2))
    extra = deep_copy(wb1.get_sheet(1))
    allSheets.append(extra)
    allSheets[-1].name = 'extra sheet file1'

    with xlrd.open_workbook("file2.xls", formatting_info=True) as rb2:
        wb2 = xlutils_copy(rb2)
        extra2 = deep_copy(wb2.get_sheet(0))
        allSheets.append(extra2)
        allSheets[-1].name = 'extra sheet file2'

    new_workbook._Workbook__worksheets = allSheets

    outputFile = "file3.xls"
    new_workbook.save(outputFile)
    os.startfile(outputFile)

      

        
        
        
      

    

The problem is that when I open my file3.xls file, I get an error message given by Excel: "File error: data might be lost." By clicking OK and checking the file, I see a lot of #CURRENCIES! errors, column width, etc., but the font and colors were not. It's great that the numbers were copied perfectly, but the text doesn't. Does anyone know what is going wrong?